1. Field of the Invention
The present invention relates to an image forming device such as a copy machine, a printer and a facsimile machine in which a developing unit, which is used for adhering a developer onto an electrostatic latent image and developing the electrostatic latent image, is inserted removably.
2. Description of the Related Art
In an image forming device, when carrying out an image forming process by adhering a developer (toner) on an electrostatic latent image carrier on which an electrostatic latent image is formed, a remaining amount of the developer decreases with the use of the developer in the image forming process. Therefore, it is necessary to replenish the developer as needed. Thus, the developing unit is formed capable of being inserted and removed with respect to the image forming device. When necessary, the developing unit is removed from the image forming device and the developer is replenished or the developing unit is replaced. However, if the developing unit is not positioned properly with respect to the electrostatic latent image carrier, the developer is not adhered evenly on the electrostatic latent image carrier and unevenness is generated in the image forming process. Moreover, if the inserted developing unit rattles, there are cases in which the developing unit makes contact with the electrostatic latent image carrier to damage the electrostatic latent image carrier.
In consideration to such drawbacks, for example, according to a first conventional image forming device, a holding member which is supported rotatably on a device frame and an urging member which urges the holding member are provided. The holding member receives a torque from the urging member and presses and holds a process cartridge in a direction in which the process cartridge is inserted. The holding member receives a torque in a reverse direction from the urging member and presses the process cartridge in a direction in which the process cartridge is removed.
According to the first conventional image forming device, by the torque from the urging member, the holding member is transferred and the process cartridge is inserted or removed. However, there is a drawback that an operator cannot confirm whether or not the process cartridge has been positioned at a proper position. That is, if the process cartridge is stopped while being transferred in the inserting direction due to some reason, an image forming process cannot be carried out normally. Therefore, there is a consideration made to increase the urging force of the urging member and to insert the process cartridge into the proper position reliably. However, if such a consideration is adopted, a collision of the process cartridge and a main frame of the image forming device becomes large when the process cartridge is inserted, and there is a possibility to cause a failure.
According to a second conventional image forming device, a guide groove is provided for guiding an inserting member, a stepped part is formed so that an interval of the guide groove becomes wide at an upper side and narrow at a lower side, and the inserting member is positioned at a set position. According to a third conventional image forming device, a pin protrudes from a side surface of a developing unit, and the developing unit is inserted while the pin is being engaged in a guide groove formed on a device frame. According to a fourth conventional image forming device, as a mechanism for sliding a shutter of a reclosed type toner cartridge, a protrusion is provided on the shutter in an inserting direction of the toner cartridge. A groove to be engaged with the protrusion is formed on a device frame. By the protrusion being engaged with the groove, the shutter can slide.
In case of a developing unit which is inserted into and removed from the image forming device, if the developing unit is not positioned properly with respect to a developer carrier such as a photoconductive drum, the developer cannot be supplied evenly to the developer carrier. However, it is necessary to prevent the developing unit from making contact with the developer carrier and damaging the developer carrier when the developing unit is inserted or removed and moves in proximity to the developer carrier. According to the second, the third and the fourth conventional image forming devices, an inserting unit is engaged with the groove formed on the device frame and the inserting unit is inserted. Accordingly, the inserted unit is guided to a set position. In particular, according to the third conventional image forming device, the developing unit is inserted into the vicinity of a photoconductive unit and there are cases in which the developing unit makes contact with the photoconductive unit.
There are proposed various countermeasures for such a unit to be inserted properly into the set position. For example, according to a fifth conventional image forming device, a slanting guide surface and a fixed member are provided so that a fixing protrusion of a replenishing developer container is engaged properly with a fixed portion at a device frame. According to a sixth conventional image forming device, a protrusion is formed on one surface of an image forming unit. In addition, a tongue part extending from the one surface on which the protrusion is formed is provided on a case of a developer supply cartridge to be inserted into the image forming unit. An opening, which can be engaged with the protrusion, is formed on the tongue part. If the developing unit is mounted without the developer supply cartridge being inserted, the protrusion is bent and the image forming unit cannot be mounted.
According to the fifth and the sixth conventional image forming devices, the image forming device includes the protrusion which is engaged with a concave part of the device frame when the unit is inserted at the proper position. However, in case of the developing unit, the developing unit is necessary to be provided at a position in proximity to the electrostatic latent image carrier such as the photoconductive drum. Therefore, there are cases in which when inserting or removing the developing unit before setting the developing unit at a proper position, the developing unit makes contact with the electrostatic latent image carrier and damages the electrostatic latent image carrier.